High frequency transformer arrangement



Oct. 24, 1944. FOSTER 2,361,187

HIGH FREQUENCY TRANSFORMER ARRANGEMENT Filed April 9, 1945 Patented Oct. 24, 1944 HIGH FREQUENCY TRANSFORMER ARRANGEMENT Raymond F. Foster, Stratford, General Electric Company,

New York Application April 9,

Claims.

My invention relates to amplifiers and in particular to wide band amplifiers such as are used in the video circuits of television receivers. It is an object of my invention to provide an improved transformer arrangement for use in such amplifiers.

A further object of my invention is to provide an improved tuning arrangement for high frequency transformers.

Another object of my invention is to provide an improved shielding arrangement for disposition between the coils of successive transformers in a plurality of coaxially aligned high frequency transformers.

Still another object of my invention is to provide an improved high frequency transformer arrangement which is readily constructed from inexpensive and available materials and which is easily assembled and adjusted to provide a desired tuning condition.

The features of my invention which I believe to be novel are set forth with particularity in the appended claims, My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing, in which Fig. 1 illustrates certain portions of a receiver embodying my invention; Fig. 2 is a diagram of certain portions of the receiver circuit embodying the transformers illustrated in Fig. 1; Fig. 3 is a modification of the transformer arrangement shown in Fig. 1; Fig. 4 is an end view of the transformer arrangement shown in Fig. 3; and Fig. 5 illustrates another modification of the invention.

In Fig. l the electron discharge devices H, l2, l3 may be employed in successive stages of a radio receiver. The device II is coupled to the device l2 by means of the transformer arrangement l4 and device [2 is coupled to device l3 by means of transformer arrangement l5. The electron discharge devices ll-l3 are supported from a metal chassis l6 by means of tube sockets H and the metal supporting rings l8 secured to the chassis l6 by means of rivets I9. Extending below the sockets ll. is the usual plurality of contacts 20.

The transformer arrangements M and I5 comprise a primary coil 22 and a secondary coil 23 magnetically coupled therewith. The coils 22 and 23 are supported in spaced coaxial relation to each other on a tubular coil form 24 of insulating material. A plurality of contact studs 25,

Conn., assignor to a corporation of 1943, Serial No. 482,501

in the form of tubular rivets, are secured to the opposite ends of tubular insulator 24. The ends of coils 22 and 23 are electrically connected by suitable leads 26, 21 to the rivets 25 by soldering, or any other desirable means. The transformer assembly is supported directly from the contacts 20 of the tube sockets ll by the substantially rigid leads 30, 3| soldered to one of the contacts 20 of each of the sockets and secured to coil form 24 by the rivets 25. Preferably, the contacts 20 of the sockets are arranged so that lead 30 is connected to the plate, or anode, contact of discharge device H and lead 3|, to the control electrode, or grid, contact of electron discharge device l2. In this manner the transformer arrangement takes advantage of the spacing which occurs between the external grid and plate electrodes of a single-ended electron discharge device, i. e., the type of electron discharge device in which all of the electrodes extend directly from the base of the device. By this arrangement, also, the axis of the tubular insulator 24 intersects the vertical axes of the devices H and I2 at right angles and the plurality of transformers l4 and I5 may be substantially coaxiall aligned.

In order to provide means for adjusting the self-inductance of the windings 22 and 23 without varying substantially the mutual inductance of this pair of windings, as well as to provide means to isolate magnetically .the windings of one transformer from those of another, a pair of metallic rings 32 and 33 is provided on each of the coil forms 24 and each of the rings 32, 33 is located opposite the outer face of a respective one of the pair of windings 22, 23. Thus, the ring 32 is supported by the insulator 24 opposite the outer face of coil 22 and ring 33 is located opposite the outer face of coil 23, The rings 32 and 33 preferably are formed of a non-ferrous material, such as aluminum. and the position of these rings upon the tubular insulator 24 is adjustable so that they may be brought closer to the coils 22 and 23 or moved farther away in order to tune the same. In this manner, each of the rings functions as a short-circuited conductive winding and operates to change the inductance of its associated coil without varying substantially the mutual coupling of the pair of coils. Moreover, this change in the self-inductance of the coils is accomplished with very slight change in the Q or quality of the associated coil. For example, when the rings are formed of aluminum, the inductance of the associated coil with very slight may be varied as much as 50% designate corresponding parts.

change in the quality of that coll. A change 01' 25% may be obtained by sliding the ring from a position approximately inch away from the coil to a position inch away. With this amount of variation in spacing, no decrease in the quality of the coil is noticed.

The rings 32 and 33 function additionally to provide a very good electromagnetic shield for the windings of the transformers l4 and I 5 so that substantially no flux lines are present at the ends of the coil form, which flux, if present at the end of the coil form 24 at the end of transformer I5, for example, would thread the windings of transformer H to cause feedback of energy from the higher to the lower stages of the amplifier.

In mounting the coils 22 and 23 on the insulator 24 and connecting the leads 28 and 21 to associated circuits, the leads 26 connected to the inner layers oi the coils are Joined preferably to those portions oi the receiver circuits which operate at potentials varying from ground potential, such as the anode and control electrode circuits, while the leads 22' connected to In this manner, the outsides of the winding 22 and 23 are relatively at ground potential to the high frequency radio currents which thread these coils and feedback between different portions of the receiver circuits is kept to a minimum.

In it, I have shown the portions of a receiver circuit which may represent, for example, the intermediate frequency amplifier circuits of a superheterodyne receiver. In the figures corresponding reference numbers have been used to The electron discharge devices is, it, i2, i3 may comprise successive stages of the intermediate frequency circuit. The winding 22 in the input circuit of device 53 may be connected to preceding portions of the r ceiver circuit, such as the radio frequency amplifiers and a first detector, and the winding in the output circuit of device 13 may be connected to a second detector circuit and supply currents to the output circuits of the receiver. The windings 22, 23 are tuned broadly to desired operating frequencies by means of capacitances 35, 38. Final adjustment of the tuning of these circuits is effected by means of the tuning rings 32, 33.

The devices iiii3 have been shown as pentodes having an anode 3'! connected to one terminal of coil 22 of the transformer, a cathode 38 connected to ground through capacitor 66 to the opposite terminal of coil 22 and through capacitor at to one terminal of coil 23. The opposite terminal of coil 23 is connected to the control electrode of the associated device. The grids 62 of the devices may be connected directly to the cathodes to act as the usual suppressor grids. The screen grid of each of the devices is connected to cathode and ground through capacitor Z-i Operating potential for the anodes and screen electrodes of the devices may be supplied from any suitable source, such as the battery d5 through decoupling resistors 46. Automatic volume control potentials may be supplied over a conductor to the input circuits or" the respective stages through grid bias resistances 48.

In the transformer arrangement shown in Fig. 3, the coil form it is shown as having threaded portions 50 and El on its opposite ends to cooperate respectively with threaded flanges 52 and 53 on the metallic rings 54 and 55. In this arrangement of the transformer. the self-inductance oi the windings 22, 23 carried on the form 24 is ad- Justed by advancing the non-ferrous metallic rings 54 and 55 along the threads 50 and 5|.

In Fig. 4 there is shown an end view of the transformer arrangement of Fig. 3. This view illustrates the slots 56 cut in rings 54 and 55 to facilitate advancing the rings along the threads on the supporting insulator by the use of any suitable tool, such as a screw driver.

In the transformer arrangement shown in Fig. 5, a pair of powdered iron tuning cores or slugs l0, 6| are provided for primary adjustment of the inductance of the windings 62, 63, 64, and the rings 66, 81 function as means to provide a secondary adjustment of the tuning of coils 62 and 65. A pair of closure members 68 and 69 are provided for the end of the tubular insulating support 10 and have shouldered portions ll, 12 which abut against the ends of insulator l0. Screws [3, l4, embedded 69 and function as means for adjusting the positions of tuning slugs 60, 6| within the coil form.

The insulator 10 is provided with a plurality of openings for the reception of suitable congectllng means, such as the rivets 25 shown in 6SK7 tubes were used for the devices l0l3, a 4700-ohm resistor was used for the resistance 45 and a 100,000-ohm resistor for the resistance 48. Using a lO0-volt supply 45 for the anodes and screen electrodes of the devices and operatamplifier is much more stable and provides better cooling for the coils 22, 23 than intermediate frequency amplifiers previously used and employing more costly transformer coils mounted in shield cans or casings. The stability of the amthan detuning action.

While I have described the rings 32 and 33 as being made of aluminum, any other non-ferrous assembled and adjustec' tuning condition.

such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a high frequency transformer, a primary coil and a secondary coil coupled magnetically therewith, dielectric means supporting said coils in spaced coaxial relation to each other, and a pair of metallic rings supported by said dielectric means in spaced coaxialirelation with said coils, each of said rings being located opposite the outer face of a respective one of said coils and being movable along the axis of said coils to vary the self-inductance of its respective coil without altering substantially the mutual inductance of said coils.

2. In a high frequency transformer, a primary coil and a secondary coil coupled magnetically therewith, dielectric means supporting said coils in spaced coaxial relation to each other, and a pair of metallic rings supported by said dielectric means in spaced coaxial relation with said coils, each of said rings being located opposite the outer face of a respective one of said coils,

be advanced along the axis of said coils to vary the self-inductance of its respective coil without altering substantially the mutual inductance of said coils.

3. In an amplifier having a plurality of stages, the combination of, a plurality of substantially coaxially aligned transformers, each of said transformers comprising a pair of magnetically coupled windings connected respectively to successive ones of said stages, means other, and means to isolate magnetically the windings of different ones of said transformers to prevent feedback between said stages and to vary and means whereby each of said ring may supporting said windings in spaced coaxial relation to each the self-inductance of individual windings of a respective transformer without varying substantially the mutual coupling of the pair of windings of said respective transformer.

4. In an amplifier having a plurality of stages, the combination of, a plurality of substantially coaxially aligned transformers, each of said transformers comprising a pair of magnetically coupled windings connected respectively to successive ones of said stages, means supporting said windings in spaced coaxial relation to each other, and means to isolate magnetically the windings of different ones of said transformers to prevent feed back between said stages and to vary the self-inductance of individual windings of a respective transformer without varying substantially the mutual coupling of the pair of windings of said respective transformer, said last means comprising a pair of metallic rings on said supporting means in spaced coaxial relation with said pair of windings, each of said rings being located opposite the outer face of a respective one of said pair of windings and being adjustsaid coils comprising cooperating threads on said and said rings.

RAYMOND dielectric means F. FOSTER. 

